Biogeography of CrocodYlians Joyce Ann Boutilier

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Biogeography of CrocodYliansJoyce Ann Boutilier
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Distribution
Crocodiles
Caimans
Phylogeny
Evolution
Alligators
Gharials
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From the beginning
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Some background

• Crocodylian ancestors first arose during the
  Mesozoic Era
• Mesozoic Era 251 mya to 65 mya

Anapsid
Diapsid
TRIASSIC 200
million years ago
JURASSIC 135
million years ago
CRETACEOUS 65
million years ago
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Ancient Distribution
?
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SUPERCROC
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The Crocodylian Body Plan

• Very successful body plan
• Eyes and nose on top of skull
• Semi-erect posture
• All four resemble each other
• However, some differences
• salt excreting organs
• snout shape

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Evolution Controversy
Traditional Hypothesis
Haemothermia Hypothesis
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The families Classification

• Order Crocodylia
• Superfamily Gavialoidea
• Family Gavialidae - Gharials
• Superfamily Alligatoridea
• Family Alligatoridae
• Subfamily Diplocynodontinae (extinct)
• Subfamily Alligatorinae- Alligators
• Subfamily Caimaninae- Caimans
• Superfamily Crocodyloidea
• Family Crocodylidae
• Subfamily Mekosuchinae (extinct)
• Subfamily Crocodylinae - Crocodiles

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Lets meet the families
Alligatoridae
Crocodylidae
Gavialidae
From the top American alligator (Alligator
mississippiensis), Nile crocodile (Crocodylus
niloticus), Indian gharial (Gavialis gangeticus)
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Family Alligatoridae
American alligator (Alligator mississippiensis)
Chinese alligator (Alligator sinesis)
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Alligatoridae
Paleosuchus palpebrosus
Paleosuchus trigonatus
Caiman yacare
Caiman crocodilus apaporiensis
Melanosuchus niger
Caiman crocodilus
Caiman latirostris
Caiman crocodilus fuscus
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Crocodylidae
C. acutus
C. moreletii
C. cataphractus
C. intermedius
C. siamensis
C. johnstoni
C. mindorensis
C. rhombifer
Osteolaemus tetraspis
C. niloticus
C.novaeguineae
C. palustris
Crocodylus porosus
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Which is which??

• Shape of the jaw
• V-shaped, pointy snouts versus U-shaped, round
  snouts
• Teeth
• Fourth tooth showing versus covered up when
  closed
• Habitat
• Special glands in their tongues work well versus
  not well means saltwater habitats versus
  freshwater habitats.

CROCODILE
ALLIGATOR
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Gharials
Family Gavialidae
Actually Crocodylidae!!
Tomistoma schlegelii False Gharial
Gavialis gangeticus Indian Gharial
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Gavialidae Controversy

• Schematic view of crocodilian
• Relationships based on
• morphological and
• (B) molecular data

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Hatchling Adult
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Modern Crocodylian
World Wide Distribution
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Modern Crocodylians Number of Species per Country
Note this does not show the actual geographic
distribution of crocodilians.
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Alligatoridae Distribution
Alligator and Caiman Range southern United
States and eastern China caimans are found in
Central America and South America
American Alligator (Alligator mississippiensis)
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Alligatoridae Distribution
China restricted to areas Around the lower
Yangzi River
Chinese alligator
(Alligator sinensis)
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Alligatoridae Distribution
Spectacled caiman (Caiman crocodilus )
Caiman Range Central America and South America
Brazil, Colombia, Costa Rica, Cuba, Ecuador, El
Salvador, French Guiana, Guatemala, Honduras,
Mexico, Nicaragua, Panama, Peru, Puerto Rico,
Surinam, Tobago, Trinidad, United States,
Venezuela
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Crocodylidae Distribution
Crocodile Range Mexico, Central and South
America, Africa, Southeast Asia, and Australia
American Crocodile (Crocodylus acutus)
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Gavialidae Distribution
Historical range of gharials India, Pakistan,
and Nepal. Numbers very low or extinct in
Bangladesh, Bhutan, and Burma. Not an accurate
representation of present distribution, which is
more restricted now.
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Climate Limitations
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Conservation
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Implications to Humans
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Why did they outlive the
dinosaurs?
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Bad Conditions?
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YIKES!
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Questions?
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CLASS REPTILIA
ORDER CROCODYLIA
FAMILY ALLIGATORIDAE Genus Alligator Alligator
mississippiensis Alligator sinesis Genus
Caiman Caiman crocodilus Caiman
latirostris Caiman yacare Genus
Melanosuchus Melanosuchus niger Genus
Paleosuchus Paleosuchus palpebrosus Paleosuchus
trigonatus FAMILY GAVIALIDAE Genus
Gavialis Gavialis gangeticus
FAMILY CROCODYLIDAE Subfamily Crocodylinae
Genus Crocodylus Crocodylus acutus Crocodylus
cataphractus Crocodylus intermedius Crocodylus
johnstoni Crocodylus mindorensis Crocodylus
moreletii Crocodylus niloticus Crocodylus
novaeguineae Crocodylus palustris Crocodylus
porosus Crocodylus rhombifer Crocodylus siamensis
Osteolamus tetraspis Subfamily Tomistominae
Genus Tomistoma Tomistoma schlegelii